The present invention relates to motion-transmitting or drive mechanisms comprising a succession of gear wheels and in particular its subject matter is a device with a high degree of safety for reducing noise produced by the couplings comprising said gear wheels.
In this description, reference will be made to the field of the wrapping and packeting machines in which such problem is particularly acute at the present state of the art.
As known, the conventional machines of the above mentioned type attain output-speed limits (about 500 wrappings per minute) which are practically insuperable in these conventional machines.
The Applicant has successfully located one of the main causes of such speed limits in systems for transmitting motion from the source to various members for wrapping products, for feeding products to be wrapped, or for feeding wrapping material.
Said machines of conventional type are in fact widely used for transmitting and distributing the motion of members of flexible nature (belts) or of discontinuous type (chains) or other like members which at high speeds, i.e. beyond well defined limits of mechanical stress are subjected to drawbacks such as, besides breakage, yielding or slackening.
It also appears that such deterioration of the motion transmission and distribution means results in incontrollable deviations from the precise limits assigned to them in the operating phases of the wrapping and feeding members.
In view of the above, the Applicant's Assignees G.D. S.p.A. have abandoned the conventional schemes by excluding from the wrapping and packeting machines the above mentioned types of motion transmission and distribution members, which have been replaced by continuously rotating gear wheel units.
Such gear wheels are arranged in succession and extend from the motion source to the various distribution zones from where the alternating and intermittent motions of the various members involved in the different operating steps are taken.
When bearing in mind, as disclosed for example in U.S. Pat. Nos. 3,670,475 and 3,948,115, that in the wrapping and packeting machines of G.D. S.p.A. the wrapping or packeting operation of the products is performed through greatly simplified operations compared with the machines of conventional type although such simplied operations are more numerous and are carried out along rather long wrapping lines, it should appear that the use of long highly noisy gear wheel trains was thus far unavoidable.
The problem of reducing such noise is particularly acute in the plants where a plurality of such wrapping and manufacturing machines operate, and the numerous attempts to eliminate such inconvenience have given poor results up to now.
Usually, the clients or definite standards in some countries require that the noise level is not higher than 80-85 dB, independently of its frequency, in working surroundings.
Said attempts above all aimed at an accurate forming of the toothings or at various expedients (for instance inclined toothings) and at the use of co-axially meshing and angularly adjustable gear wheels to avoid even minimum play between the gear wheels.
Moreover, the attempts to solve such problem by using gear wheels having different physical characteristics (hardness, elasticity, etc.) in the same motion transmission system, although effective in reducing the noise, are detrimental in case of wear of the gear wheels which are less wear and fatigue resisting.
The need thus exists for the damaged gear wheels to be replaced and for complicated and laborious operations to be preformed in order to restore the coordination of the operating stages of the machine members involved in the various productive operations.
An object of the present invention is then to provide a device capable of reducing to a low level the noise produced by the meshing engagement between motion transmission and distribution gear wheels in said wrapping and packeting machines.
Another object of the present invention, in conformity with the preceding object, is to provide a device of the above mentioned type and with a high degree of safety.
Another object of the present invention is to provide a device of the above mentioned type which is extremely simple and economic in view of the results obtained with it.